1. Field of the Invention
The present invention relates to a conveying device and a printing apparatus including the conveying device.
2. Description of the Related Art
In a known printing apparatus, a sheet that has undergone printing is conveyed while being nipped between a set of discharge rollers (conveying rollers) and a set of spurs (rotating bodies). The spurs each have sharp teeth (edges) and rotate while biting the surface of the sheet.
Such a conveying device is disclosed by Japanese Patent Laid-Open No. 2006-347119. The conveying device includes a spur holder that supports spurs while allowing the rotation of the spurs and that prevents the spurs from moving in a thrust direction (axial direction), whereby the spurs are supported in such a manner as to stand substantially vertically to the sheet.
The conveying device disclosed by Japanese Patent Laid-Open No. 2006-347119 is intended to support each of the spurs as vertically as possible. To allow the spur to rotate smoothly, however, a clearance is necessarily provided between the spur and the spur holder. The spur can take various positions within the clearance. That is, as illustrated in FIG. 8 of Japanese Patent Laid-Open No. 2006-347119, the spur inclines in the horizontal direction to some extent when seen from the downstream side in the direction of sheet conveyance.
In some cases, the sharp teeth of the spur each have an asymmetrical shape, when seen from the downstream side in the direction of sheet conveyance, with only one side thereof having a slope and the opposite side thereof not having a slope. This is because of the easiness in manufacturing a sharp edge of the spur.
If such a spur having asymmetrically shaped teeth is supported by the spur holder disclosed by Japanese Patent Laid-Open No. 2006-347119, marks that are made when the teeth of the spur bite the surface of the sheet may become large depending on the direction of inclination of the spur. Consequently, the damage to the sheet may increase. Such a mechanism will be described in detail in the description of embodiments.
The present invention is based on the recognition of the above problem and provides a conveying device in which the damage to a sheet that is caused by a spur is reduced.